Question 261: Waves Optics

Question

Three polarised sheets are co-axially placed. Pass axis of polaroids 2 and 3 make $30^{\circ}$ and $90^{\circ}$ with pass axis of polaroid sheet. If $\mathrm{I}_0$ is the intensity of unpolarised light entering sheet 1 , the intensity of the emergent light through sheet 3 is

$$ \left(\cos 30^{\circ}=\sqrt{3} / 2, \cos 90^{\circ}=0, \cos 60^{\circ}=1 / 2\right) $$

Accepted Answer

According to Malus' law,
$$ \mathrm{I}=\mathrm{I}_0 \cos ^2 	heta $$
When beam passed through polaroid 1 ,
$$ \mathrm{I}=\frac{\mathrm{I}_0}{2} $$
When beam passed through polaroid 2,
$$ \begin{aligned} & \mathrm{I}_2=\frac{\mathrm{I}_0}{2} \cos ^2 60^{\circ} \ 	herefore & \mathrm{I}_2=\frac{\mathrm{I}_0}{8} \end{aligned} $$
When beam passed through polaroid 3,
$$ I_3=\frac{I_0}{8} \cos ^2 30^{\circ}=\frac{I_0}{8} 	imes\left(\frac{\sqrt{3}}{2}ight)^2=\frac{3 I_0}{32} $$

Answer

zero

Answer

$\frac{3 \mathrm{I}_0}{32}$

Answer

$\frac{3 \mathrm{I}_0}{8}$

Answer

$\frac{3 \mathrm{I}_0}{16}$

Waves Optics

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